Hello, and welcome to Parasites: Helminths.
We are going to take a deeper look into some
helminthes that cause human infections. And
after you listen to this lecture, you will
understand the lifecycles of helminths such
as ascaris, hookworm, trichinella and schistosomes
and how they are transmitted to humans. You
will be familiar with the pathogenesis of
the different forms of helminth infections,
and you will know how to prevent and treat
infections with helminths.
So again these are worms, these are multicellular
animals or metazoa. We've been talking about
protozoan parasites, single celled parasites,
now we move to multicellular parasites, metazoa.
And the helminths are worms, are divided
into two general categories; we have the roundworms,
also known as nematodes or non-segmented roundworms,
and then we have flatworms, these are asymmetric
in cross section. Roundworms and flatworms.
Worms reproduce sexually; there are male and
female worms that mate to produce offspring.
Again we're talking about worms in general;
we're talking about roundworms, nematodes,
non-segmented roundworms. An example of this
is shown right here. In this photograph, ascaris
lumbricoides, that's a typical worm we'll
talk about and then we'll talk about the hookworms,
another kind of nematode or non-segmented
roundworm. Helminths can also be divided into
flatworms as I said, these are asymmetric
in cross-sectioned, a photograph of such
a flatworm is shown here. These are segmented
flatworms, or cestodes or tapeworms, again
so the flatworms can be further divided. These
can be millimeters to meters in length and
there are non-segmented flatworms also called
trematodes or flukes. These are typically
short, with non-segmented bodies and we will
talk about an example of this as well and
that would be schistosoma.
Alright, back to roundworms. Again helminths,
nematodes are roundworms, the example is ascaris